Heavy oil and bitumen resources are supplementing the decline in the production of conventional light and medium crude oils, and production from these resources is steadily increasing. Pipelines cannot handle these crude oils unless diluents are added to decrease their viscosity and specific gravity to pipeline specifications. Alternatively, desirable properties are achieved by primary upgrading. However, diluted crudes or upgraded synthetic crudes are significantly different from conventional crude oils. As a result, bitumen blends or synthetic crudes are not easily processed in conventional fluid catalytic cracking refineries. Therefore, in either case further processing must be done in refineries configured to handle either diluted or upgraded feedstocks.
Many heavy hydrocarbon feedstocks are also characterized as comprising significant amounts of BS&W (bottom sediment and water). Such feedstocks are not suitable for transportation by pipeline, or refining due to their corrosive properties and the presence of sand and water. Typically, feedstocks characterized as having less than 0.5 wt. % BS&W are transportable by pipeline, and those comprising greater amounts of BS&W require some degree of processing or treatment to reduce the BS&W content prior to transport. Such processing may include storage to let the water and particulates settle, and heat treatment to drive off water and other components. However, these manipulations add to operating cost. There is therefore a need within the art for an efficient method of upgrading feedstock having a significant BS&W content prior to transport or further processing of the feedstock.
Heavy oils and bitumens can be upgraded using a range of processes including thermal, hydrocracking, visbreaking, or catalytic cracking procedures. Several of these processes, such as visbreaking or catalytic cracking, utilize either inert or catalytic particulate contact materials within upflow or downflow reactors. Catalytic contact materials are for the most part zeolite based, while visbreaking typically utilizes inert contact material, carbonaceous solids, or inert kaolin solids.
The use of fluid catalytic cracking (FCC), or other units for the direct processing of bitumen feedstocks is known in the art. However, many compounds present within the crude feedstocks interfere with these processes by depositing on the contact material itself. These feedstock contaminants include metals such as vanadium and nickel, coke precursors such as (Conradson) carbon residues, and asphaltenes. Unless removed by combustion in a regenerator, deposits of these materials can result in poisoning and the need for premature replacement of the contact material. This is especially true for contact material employed with FCC processes, as efficient cracking and proper temperature control of the process requires contact materials comprising little or no combustible deposit materials or metals that interfere with the catalytic process.
To reduce contamination of the catalytic material within catalytic cracking units, pretreatment of the feedstock via visbreaking, thermal or other processes, typically using FCC-like reactors, operating at temperatures below that required for cracking the feedstock have been suggested. These systems operate in series with FCC units and function as pretreaters for FCC. These pretreatment processes are designed to remove contaminant materials from the feedstock, and operate under conditions that mitigate any cracking. These processes ensure that any upgrading and controlled cracking of the feedstock takes place within the FCC reactor under optimal conditions.
Several of these processes have been specifically adapted to process “resids” (i.e. feedstocks produced from the fractional distillation of a whole crude oil) and bottom fractions, in order to optimize recovery from the initial feedstock supply. The disclosed processes for the recovery of resids, or bottom fractions, are physical and involve selective vaporization or fractional distillation of the feedstock with minimal or no chemical change of the feedstock. These processes are also combined with metal removal and provide feedstocks suitable for FCC processing. The selective vaporization of the resid takes place under non-cracking conditions, without any reduction in the viscosity of the feedstock components, and ensures that cracking occurs within an FCC reactor under controlled conditions. None of these approaches disclose the upgrading of feedstock within this pretreatment (i.e. metals and coke removal) process. Other processes for the thermal treatment of feedstocks involve hydrogen addition (hydrotreating), which results in some chemical change in the feedstock.
Methods are known for assisting in the recovery of heavy oils from oil production fields. For example, one method used for removing bitumen from oil-sands is an oil extraction process known as Steam-Assisted Gravity Drainage (SAGD). SAGD uses steam generated from a source of energy, such as natural gas, to reduce the viscosity of the solidified bitumen and make it transportable through a pipeline. This method requires the introduction of natural gas to the oil field. Furthermore, the amount of natural gas needed to extract a barrel of bitumen from oil sands in energy equivalents is about 1 to 1.25 GJ. Due to fluctuations in the price of natural gas, the cost of obtaining a barrel of bitumen using SAGD and natural gas may escalate over time. It is therefore desirable to have an alternate source of energy for generating steam that is inexpensive, replenishable and in close proximity to the site of a bitumen production facility to control the cost of operations and allow the facility to operate with little or no natural gas.
The present invention is directed to a method for upgrading heavy hydrocarbon feedstocks, for example but not limited to heavy oil or bitumen feedstocks, to produce a bottomless product or other upgraded product as desired based on market or consumer requirements or preferences. The method utilizes a short residence-time pyrolytic reactor operating under conditions that upgrade the feedstock and a vacuum tower. The feedstock used within this process may comprise significant levels of BS&W and still be effectively processed, thereby increasing the efficiency of feedstock handling. Furthermore, a portion or all of the energy requirement of the oil field may be addressed by removing some of the partially upgraded product, thereby reducing or eliminating the need for externally supplied natural gas.